Building-Integrated Solar Energy Systems by Robert E. Parkin

Author of Building-Integrated Solar Energy Systems PDF

Robert E. Parkin received his Ph.D. degree from Imperial College, University of London, in 1965. He has spent most of his professional life in academia.

He joined the Electrical Engineering faculty at the University of Massachusetts, Lowell, in 1982, transferred to the Mechanical Engineering Department in 1991, which better represented his research interests in manufacturing theory and robotics, and is presently Professor of Mechanical Engineering.

He has held several administrative positions, including President of the Faculty Senate and President of the Massachusetts Society of Professors.

He presently serves as Chair of the College of Engineering Personnel Committee, and Chair of the Research and Development Committee of the Faculty Senate. His primary area of research is now solar energy. He is the Graduate Coordinator of the Renewable Energy degree programs at UMass Lowell.

Solar Energy Systems Contents

Energy Sources, Energy Uses, and Global Warming

The Internal Environment of a Residence

Heat Flow from a Residence

Residential Construction Techniques

The Seasons and Solar Angles

Transmission of Light through the Atmosphere

Solar Gain and Solar Attenuation

Transmission of Solar Energy through Glazing

Climate and the Siting of a Solar Structure

Solar Structures from Early to Modern

Passive Solar Collection

Non-Concentrating, Active Solar Collectors

Photovoltaic Panels

Smart Grids, FiTs, and Net Metering

Architectural Considerations for Capturing Solar Energy

Methods of Energy Storage

Index

Preface to Building-Integrated Solar Energy Systems eBook

The language of science is broad and needs to be to cover an immense array of subjects: in size from the molecular to the cosmic scale, from the mass of a hydrogen atom to that of the universe

In times from nanoseconds to billions of years; in electrical energy to describe the communication to and from a single cell in a human body to crushing hydrogen atoms into helium to produce electrical power by nuclear fusion; in temperatures from absolute zero to the center of a star.

The metric system was developed at the time of the French Revolution. It established the meter as the unit of length and the kilogram as the unit of mass. Subsequently, it added the second as the unit of time and became the MKS system.

Eugene Niemi, a colleague of mine at UMass Lowell, describes the MKS (SI) system as consistently inconsistent. He called it that since it stubbornly clings to 360 degrees in a circle and 24 hours in a day.

He also called the English system consistently inconsistent, with its reliance on historically archaic definitions. What are the anchor units we need to live with? The day is a physical reality, but why describe it as 24 hours? The Earth year is also real at 365.2425 days. pi=3.141592 is also real, as is the exponential e=2.71828.., but most other measures are artificial constructs of archaic origin.

There are problems with the MKS system. In particular, as far as the scope of this text is concerned, the units may not be appropriate. The unit of time S does not work as well as the hour, which even in the decimal-based SI system is 3600 seconds.

The electrical power we buy from the utility company is measured in kWh, kilowatt-hours. The standard size sheet of plywood in North America and in Europe is 4’×8’, 4 feet by 8 feet, where the foot length is approximately 0.3048 meters; the Europeans call the same size 2440mm x 1220mm (they put the larger dimension first, the opposite to the U.S. convention).

Efforts were made in 1948 to expand the MKS system, and in 1960 the Systeme International d’Unites was established.

It now has seven measures, adding the ampere (electrical current), the kelvin (unit of temperature), the mole (unit of substance at the atomic level), and the candela (unit of light intensity). It is now called the SI system.

It is decimal-based, and larger or smaller units are indicated with a prefix, so cm means centimeter, and km means kilometer.

The language of science is relatively new, and this can lead to contradictions and possible confusion. Luckily, in a confined subject such as solar energy one can focus on the terms needed, and omit other terms that may be indispensable in other branches of science.

We will use the tonn (1000 kg), try not to use the long ton (2240 pounds or 1016 kg) or the short ton (2000 pounds), will use the pascal and the bar for pressure and try and avoid the psi (pound per square inch), will use the watt W and will try (unsuccessfully) to avoid the BTU (British Thermal Unit, 0.2931 Wh)

And will rarely use the unit of energy the joule. What is the underlying philosophy in this text? I like diagrams that convey the maximum amount of information in as simple a way as possible. I could not have prepared my manuscript without MATLAB ®.

Most of the response curves in this book were rendered using MATLAB. About 100 MATLAB files are on a CD included with this book.

Many of the exercises for each chapter can be answered with MATLAB. Virtually all formulae I use are derived from first principles. I favor a vector-based notation, in contrast to the direction cosines that most authors in solar engineering use.

The advantages of vectors over direction cosines include simpler notations and far simpler diagrams. Perhaps I gravitated to the vector notation because I could not make sense of the diagrams that others use.

Why building-integrated? Often solar installations are far too expensive, and the reason is simple: the system is installed on an existing structure that was constructed with no consideration for a future solar system.

For example, a number of companies offer flat plate collectors that come with glazing, insulation, a frame, and a support system, and cost about $700/m2 installed.

However, if the roof structure was designed to accept those flat plates, the glazing is the roof, the frames are the rafters, and the insulation is the insulation of the house, and there is no need for an additional support system.

Thus, the additional cost above normal construction costs is for the flat plate collector panels and associated piping, far less than the $700/m2.

As another example, Fraunhofer, the German non-profit, recently introduced PV panels that glue on top of existing roof shingles, and need no frame or support system. Installed cost is about $1.50/watt, compared to the typical $4.90/watt.

In the 1970s I designed and built a number of solar structures, mostly single-family houses. I favored passive solar at the time, and to some extent still do. It is cost-effective and architecturally pleasing.

The last house I built, in 2010 for my daughter’s family, has semi-passive solar with a central atrium to collect the heat, and a fan/duct system to push the heated air into a rock storage system beneath the floor. It has 3.8 kW of PV on the roof and is grid-connected.

It also has geothermal heating and cooling, an experimental system that experts said would not work: In fact, it works better than anticipated. The chapter development in this book is intended to be logical. The first chapter defines the energy problem we face.

Subsequent to the industrial revolution we used an incredible amount of energy in three sectors industrial, transportation, and in buildings. It is the energy use in buildings, particularly residences, that is the central theme here.

If the objective is to use solar energy to produce most, or all, of the energy needed in a residence, one must start by defining what is needed for human comfort (Chapter 2), then delve into heat losses from a structure (Chapter 3).

Materials used in residential construction and construction techniques themselves are the subject, of Chapter 4.

The vector-based geometry of the motion of the Earth around the Sun following Kepler’s laws in Chapter 5 is, I believe, an important contribution to the field of solar engineering.

Without loss of generality, one can assume that the Sun and the Earth lie in the x-y plane, so then the axis of rotation of the Earth is a known vector that I call the obliquity vector. I do not know how declination tables were constructed.

It seems probable that they are based on celestial observation. There are papers that purport to derive declination, but they do not carry it to a conclusion and an actual table.

In Chapter 5 a derivation for declination is presented based on the Kepler’s laws, but there is a discrepancy with the established tables that is troubling. Even further, a similar technique to derive “equation of time” tables finds an even bigger discrepancy with published tables.

In this latter case, I have presented evidence of errors in this table, realizing that perhaps this is provocative. The transmission of light through the atmosphere as defined by Planck’s law and attenuating factors such as oxygen, ozone, and water vapor is the subject of Chapter 6.

The solar constant is 1366 W/m2, which is reduced to about 880 W/m2 at the Earth’s surface. The unanswered problem is to explain where the 486 W/m2 went.

A partial answer is that it has been scattered, of which Rayleigh scattering is the most important constituent. Chapter 7 attempts to further identify the factors responsible for the loss of 486 W/m2.

There is an inverse relationship between beam (direct normal) radiation and diffuse radiation. That is, diffuse is low when the beam is high, and diffuse increases and beam decreases as clouds and aerosols increase in the atmosphere until a certain point and then diffuse decreases until fully occluded conditions occur.

A problem with most models for solar attenuation is that they do not provide a rationale for their development. Attempts here to correct this deficiency were not successful, but at least the problem is defined and possibly will be of use in future work, either by me or others.

Chapter 8 provides a comprehensive treatment of the transmission of light through glass. It ends with a discussion of LoE glass, sometimes called low-E or Low-E glass, including recent developments.

There is a major problem with the requirement in the United States that all window glass be LoE, which is the kiss of death for passive solar collection. SHGC (Solar Heat Gain Coefficient) through LoE glass is low.

It makes sense to use LoE glass in windows not facing the equator since solar gain through them is probably unwanted, but glass facing the equator has little, or no, solar gain in summer but maximum solar gain in winter. Chapter 9 defines climate and uses three measures.

The first is the universal Koppen climate classification based on vegetation, and the second is the climate zone classification used in the United States predominantly to advise gardeners as to which plants will survive.

These are gross measures and have limitations in determining energy flow to and from a residence in a particular location.

The third measure is the heating and cooling degree days, which is a more satisfactory measure since there are extensive individual sites that measure temperature daily across the populated world.

It was found that a satisfactory way to reduce the random changes in temperature was to use monthly averages for each site and to collate the data over a number of years.

The suitability of a site to accept a solar structure should be ascertained before building commences, and this is included in Chapter 9.

In particular, can the structure face the Sun without impediments, such as other structures or trees that are in the neighbor’s yard, blocking the Sun and such that they cannot be removed? The angles and dimensions needed are discussed. Solar structures are considered in Chapter 10.

What makes a house heated by the Sun successful is glass. The large sheet of glass is a recent invention. There are very good architectural and energy reasons to employ passive solar radiation, and these are discussed in Chapter 11.

The Passivhaus houses in Germany and Austria have been highly successful, even though the climate is not as welcoming for passive solar heating as are vast swaths of the United States. Active solar systems for residential use are explored in Chapter 12.

Photovoltaic cells from first to the third generation are treated in Chapter 13, and that chapter ends with a discussion of perovskite cells that could become the savior of our planet by moving us into a hydrogen economy.

The grid and the connection of renewable energy power generators are discussed in Chapter 14. The present-day, utility run, the power grid is an anachronism.

It has barely changed in 100 years, but with the rise of distributed generation from renewables, such as wind and PV, it is evident to the knowledgeable observer that the investor-owned utility company will not survive in its present form.

Architectural requirements for building-integrated solar elements are considered in Chapter 15. The energy storage problem is discussed in the last chapter, with the limitations of battery technology given full voice.

Who will use this book? This is a textbook for seniors or graduate students in engineering, physics, or chemistry. It is too technical for students in humanities or social sciences, or even biology. There are exercises for every chapter.

The students in these classes must have access to MATLAB; not a problem as MATLAB is a requirement in most engineering environments.

It is also intended to be a reference book for working engineers in the solar field, and for solar system designers and installers.

Coding experts will find much to criticize regarding my programming skills. I was never into reverse Polish notation, although it saves keystrokes on a handheld calculator. In MATLAB I can achieve the result I want, although the code is not pretty.

My excuse is that when I press the save and run button, the output is produced in a fraction of a second, and the fact that additional electrons had to work harder does not concern me. Of all subjects covered, the one that gives me the greatest problem is that of heat transfer.

I rely on ASHRAE Fundamentals and tend to doubt formulae with all those numbers Nussault, Reynolds, Prandtl that are empirically based.

This book is definitely not attuned to the tropics, or to a Mediterranean climate. Perhaps one could say it is applicable to latitudes 30° to 55°, both south as well as north.

And this requires a word of apology to the southern hemisphere reader for the northern-centric language that permeates throughout. I do it for simplicity, and no slight is intended. Finally, we live and work in a connected world where the Internet is an essential part.

No longer do we use printed telephone books, but I do confess that I rely on a printed edition of the Oxford English Dictionary. The ease with which key words enable a browser to instantly bring up the information sought makes an extensive bibliography unnecessary.

I trust this does not lead the reader to assume that this work is weak in scholarship. I include essential references at the location needed rather than as a list at the end of each chapter, eliminating the discontinuity of flicking through pages to find reference number 73.